Epitaxial growth of ZnO films by helicon-wave-plasma-assisted sputtering

The epitaxial growth of ZnO films on Al2O3 (0 0 0 1) substrates have been achieved at a low-substrate temperature of 400 °C by using a helicon wave-plasma-assisted sputtering technique. X-ray diffraction θ–2θ scan, ω scan and φ scan indicate that the ZnO films have a good c-axis orientation and in-plane epitaxy. The photoluminescence measurement of the films shows that there is only a strong emission peak at 384 nm, and no visible emission related to the structural defects can be detected. A strong absorption in the ultraviolet region and a high transparence of over 85% in visible region are obtained from the optical absorption measurements. Hall-effect measurement reveals that the mobility of the deposited films is 5.0 cm2/V.s. All above results demonstrate that this newly developed sputtering technique provides a flexible and powerful technique for the growth of high-quality epitaxial ZnO films.